🚀 go-pugleaf

In article <CARLTON.92Oct5110856@scws8.harvard.edu> carlton@scws8.harvard.edu (david carlton) writes:

   Why does SML support functions of multiple arguments using both tuples
   and curried functions, anyways?

1. All functions in SML take one argument. Thinking of "functions of
multiple arguments" results in confusion of the sort you show in your
questions.

2. SML supports curried functions because in some contexts they are
	nice to use.

3. Tuples in SML are merely glossed-over record types:
	(42,true,"foo")     = {1 = 42, 2 = true, 3 = "foo"}
	int * bool * string = {1 : int, 2 : bool, 3 : string}
   ("1", "2", and "3" on the RHS are labels for record elements)

   [...]. And how much of a problem is it in practice?

None at all in my experience.

   [...] Also, what sorts of order-of-evaluation constraints does SML
   impose?  If you are compiling "f g h", say, and the compiler can't
   prove that evaluating "f g" won't have side effects, does it have
   to evaluate "f g" before evaluating "h"?  And is it required to
   evaluate "f" before "g"?

Yes to both questions, for a single reason, rules 112-118 in the
Definition require that in function applications, the function should
be evaluated before the argument. This applies to the "f g h"
question, because this is an application of the function value "f g"
to the argument "h".

Nick Haines nickh@cmu.edu